Pen-type injector having an electronic control unit

ABSTRACT

An injection device for injection of a medicament from a first medicament cartridge ( 40 ) is disclosed. The injection device comprises a drive mechanism ( 42 ) for selectively dispensing the medicament from the first medicament cartridge ( 40 ), a dial dose mechanism ( 12, 14 ) by which a user may determine a required dose of medicament to be dispensed, an electronic control unit for controlling the operation of the drive mechanism ( 42 ) in response to the dial dose mechanism ( 12, 14 ) and a display panel ( 10 ). When an insufficient amount of medicament remains in the first medicament cartridge ( 40 ) to enable the required dosage to be dispensed, the insufficient amount of medicament may be dispensed at the discretion of the user, the electronic control unit storing a value corresponding to a difference between the required dose and the insufficient amount of medicament, the value being presented to the user on the display panel ( 10 ) as a first amount of medicament to be dispensed from a replacement medicament cartridge following replacement of the first medicament cartridge ( 40 ) with the replacement medicament cartridge.

[0001] The present invention relates to improvements in an injectiondevice, and in particular to improvements in a portable injection devicefor dispensing controlled quantities of a medicament.

[0002] Typically such injection devices are used by those suffering fromdiabetes to administer a dose of insulin or insulin-type medicine tothemselves. It will be understood that such injection devices aresuitable for the injection of other medicines.

[0003] At one time, such doses were administered by use of a disposablesyringe; the syringe first being filled from a separate phial or othercontainer and then used to inject the dose. However, there were a numberof difficulties in such an arrangement. In particular, such anarrangement was not suitable for the infirm. For others, the socialstigma associated with such syringes made their public use problematic.

[0004] To overcome these difficulties a number of so-called pen-typeinjectors have been developed. These devices are small, being capable ofbeing carried in a jacket pocket or the like and allow a number of dosesto be obtained from a cartridge or ampoule contained within theinjector. The present invention has particular application to suchpen-type injectors.

[0005] While such pen-type injectors are a considerable improvement upondisposable hypodermic syringes, problems nevertheless remain. It is anadvantage of the present invention that it eliminates, or at leastsubstantially reduces such problems. The present invention also providesfor improved ease of use and improved interaction with a user.

[0006] The invention will now be described, by way of example only, withreference to the accompanying drawings; in which:—

[0007]FIG. 1 shows a plan view of a pen-type injector in accordance withthe present invention;

[0008]FIG. 2 shows a similar view to FIG. 1 with an end cap of theinjector omitted; and

[0009]FIG. 3 shows a cross-sectional view of the injector of FIGS. 1 and2.

[0010] Referring first to FIGS. 1 to 3, there can be seen a pen-typeinjector 2 in accordance with the present invention. The injector 2comprises a main housing 4 to which is releasably secured an end cap orcover 6.

[0011] At a first end of the main housing 4 there is provided a controlpanel region 8. This region includes a display panel 10, typically a LCDdisplay, and a first dose button 12 and a second dose button 14, thefirst and second dose buttons being operated to increase or decrease adose of medicament to be delivered. The control panel region 10 in theillustrated embodiment also includes an arm button 16.

[0012] At the first end of the main housing there is also provided adispense button 18. Preferably, when not depressed, the dispense button18 is flush with the main housing 4.

[0013] Along a longitudinal axis of the injector 2, to each side of thecontrol panel region 10 are provided a number of grooves or recesses 20.These aid in the gripping of the injector 2 by a user.

[0014] At a second end of the main housing 4 a needle unit 22 isreleasably secured to the main housing. The second end of the mainhousing 4 is also provided with a shaped portion 24.

[0015] In use a cartridge 40 or ampoule of medicament is stored in thehousing 4 behind the shaped portion 24. For preference, the shapedportion is transparent to permit the cartridge 40 to be seen by a user.

[0016] A primer button 26 is also provided on the second end of thehousing 4. It will be understood that when the end cap 6 is in placeover the second end of the housing, it will not be possibleinadvertently to depress the primer button 26 or to be pricked by theneedle unit 22. A cover detection switch 28 may also be included at thesecond end of the main housing 4 to detect whether the end cap or cover6 is in place or not.

[0017] In FIG. 3, there can be seen a priming contact 30, an arm contact32, a first dose contact 34 and a second dose contact 36 correspondingto the respective buttons. A dispense contact 19 corresponding to thedispense button 18 is also shown.

[0018] With reference to FIG. 3 it may be seen that there is provided asuitable location for a power source 38 such as a battery or batteries.There is also a suitable region in which a cartridge 40 or ampoule ofmedicament is to be located. This region may be accessed by way of theremovable shaped portion 24 of the main housing 4 to allow forreplacement of the cartridge 40 or ampoule as required by the user.

[0019] In a third region of the main housing 4 there is provided a drivemechanism 42 which operates from the power source 38 and acts upon thecartridge 40 or ampoule of medicament.

[0020] The cartridge 40 or ampoule comprises a container 44 or sleeveclosed at one end by a cover 46 at a head end thereof, and sealed at theother by a movable bung 48 or stopper. When in position, the needle unit22 pierces the cover 46 and movement of the bung 48 towards the cover 46will cause the medicament contained within the cartridge 40 or ampouleto be expelled. The cartridge may be a 3 ml cartridge in accordance withISO/FDIS 11608 Part 3, or any other suitable cartridge to suit theinjector.

[0021] Movement of the bung 48 or stopper is caused by movement of apiston or plunger 50 forming a part of the drive mechanism 42. Thepiston or plunger 50 is movable between a first fully withdrawn position(not shown) which allows for the replacement of the cartridge 40 orampoule and a second fully extended portion in which as much medicamentas possible has been expelled from the cartridge 40 or ampoule. An endstop switch 52 may be provided in the main housing 4 to detect when thepiston 50 is in the fully withdrawn position. Tripping of the switch endstop 52 may release a catch or other fastening device to allow access tothe main housing 4 for replacement of the cartridge 40.

[0022] The drive mechanism 42 is operated by a motor 54 under thecontrol of an electronic control unit (not shown). The motor 54 shouldbe reversible in order to allow the piston 50 to be moved between thefirst and second positions. In FIG. 3, the motor 54 can be seen to drivethe piston 50 by way of a gear train 42, such that rotation of a thirdrotor 58 causes the piston 50 to be moved in relation to the third rotor58.

[0023] Preferably, the user can feel the vibration of the motor 54 andthe associated drive mechanism 42 and/or hear them in operation. In thisway an added degree of confidence in the fact of the operation of theinjector 2 is provided to the user.

[0024] The functionality of a pen-type injector in accordance with thepresent invention will now be described, in particular with reference toFIGS. 1, 2 and 3.

[0025] The injector 2 is provided with an electronic control unit. Theelectronic control unit is coupled both to the drive mechanism and auser interface. The user interface includes the display panel 10 as wellas the user operable buttons (and associated contacts). The electroniccontrol unit is microprocessor based. Either volatile or non-volatilememory may be used for storage of ‘dose history’ and patient specificinformation.

[0026] The electronic control unit is preferably powered from theinjector power source 38.

[0027] The injector 2 preferably also includes a port for communicationbetween the electronic control unit and an external apparatus such as apersonal computer.

[0028] The injector 2 also has a priming detection facility, (such as atilt switch or accelerometer) to identify when the injector 2 isinverted. On detection of an inverted position (needle up) the injector2 will automatically change state to be ready for priming. Priming maybe initiated by depression of the primer button 26 to cause a fixedsmall dispense action. The electronic control unit may cause a speakerto sound when the primer button 26 is depressed.

[0029] The primer button 26 is inactive at all other times. When theprimer button 26 is active, all other buttons in the control panelregion are inactive, that is those buttons which are to be used to setor dispense a dose.

[0030] The electronic control unit may cause a speaker to sound when thearm button 16 is depressed for a sufficient period of time to provideaudible feedback for the user.

[0031] The function of the arm button 16 is to make the dose button 18active. The arm button is preferably held down for a predeterminedperiod of time before the injector 2 becomes armed. The armed status mayadditionally be shown on the display panel 10. The functionality of thearm button is preferably linked to the cover detection switch 28 suchthat the arm button 16 will only function to arm the injector 2 when thecover 6 is not present.

[0032] Additionally, in a preferred embodiment, a clock within theelectronic control unit will detect whether the dose button 18 has beenpressed within a specified time interval following arming of theinjector 2. If the dose button 18 has not been depressed within thespecified time interval the electronic control unit will disarm theinjector 2. Alternatively, if the arm button is depressed a second timewithin a predetermined time period by the user, the injector will bedisabled.

[0033] In an alternative embodiment, the dose button 18 may function asboth a prime button and the dose button. When the priming detector isactuated, by the injector 2 being oriented needle up, the dose button 18would change function to that of the prime button of the previousembodiment.

[0034] The buttons of the injector 2 are preferably tactile in nature toprovide sensory feedback to the user.

[0035] The display panel 10 is typically an LCD display and will providealphanumeric and graphical information relating to the operation of thedevice. The display panel 10 preferably indicates the selected dosequantity, the previous dose quantity and the time elapsed since theprevious dose was administered. Typically, the time elapsed since theprevious dose is limited to a time period within the preceding 48 hours,though other time periods are possible.

[0036] Additional information which may be displayed includes:

[0037] that the injector is armed and ready to dispense (graphical)

[0038] that the injector is dispensing (graphical)

[0039] that the injector has dispensed the selected dose and that a usershould wait before removing the needle from their body

[0040] that this waiting period has elapsed

[0041] the dose history, typically for the last 48 hours, in terms ofthe dosage taken and the elapsed time between doses

[0042] the quantity of medicament remaining in the cartridge, preferablyin terms of dosage units of the medicament.

[0043] that the device is in the priming position (either in addition toor instead of the acoustic indication noted above)

[0044] the speaker volume setting, for example high, low or muted.

[0045] that the injector is nearing the end of its life (for example abattery power level indication—graphical or countdown in terms of thenumber of days or complete operating cycles to a predetermined expiry ofthe product life—alphanumeric).

[0046] that the needle is probably blocked

[0047] that replacement of the cartridge 40 is in progress

[0048] that the dose selected is the maximum available in the cartridge40

[0049] that the maximum dose available is less than the dose expected.

[0050] The display panel 10 may offer a user a choice of languageoptions as appropriate for the market and/or user. The text displayedmay include that noted above and/or further information. The languageoption may be pre-programmed or selectable by a user. The user maypreferably select the language option by means of a menu provided on thedisplay panel 10.

[0051] The currently selected dose value, the previously used dose valueand the time (in hours) since the previous dose was dispensed, may allbe shown clearly at the same time, in large, easy-to-read characters onthe display. Preferably, the display is also provided with a backlight.

[0052] The display 10 preferably provides a graphical indication thatthe selected dose is being dispensed. This may be achieved, for example,as either an animated graphic or a countdown (or a combination of both).

[0053] The control buttons have a number of functions. The dose buttons12,14 allow a user to select a desired dosage. The dose arm button 16allows a user to confirm selection of a desired dosage. The first dosebutton can increment the dosage level and the second dose button candecrement the dosage level. The dose dialling buttons 12,14 may bepressed down (and held for a short time, 1-2 seconds) to re-set a dosevalue to zero. The user can then dial up (or down) in single (or half)increments.

[0054] The dose dialling buttons 12,14 are intended to be pressed oncefor a single (or half) increment in the selected dose value. In analternative embodiment, pressing and holding one of the buttons willcause the dose value to start to scroll (up or down) in order to changethe dose size more rapidly.

[0055] The dispense button 18 allows a user to initiate dispensing ofthe dosage. The primer button 26 dispenses a unit of dosage from thecartridge 40. Thus, if any air is trapped in the injector 2 this can beexpelled by use of the primer button 26. A door release catch isprovided to allow access to the cartridge 40.

[0056] Since the cartridge 40 is of a standard size, each cartridge 40will be emptied by an identical travel of the plunger driven by thedrive mechanism. Once the plunger 50 is in the fully extended position,the cartridge 40 is known to be empty and an indication of this will beprovided to the user.

[0057] When the door release catch is operated for the emptied cartridge40 to be removed the drive mechanism 42 is operated to reverse a leadscrew 60 to withdraw the plunger 50 until the lead screw 60 strikes theend stop switch 52 which is provided at a known reference point.

[0058] When a new cartridge 40 is detected, for example by way of acontact switch (not shown), and the door release catch closed, theelectronic control unit advances the lead screw 60 until the plunger 50strikes the cartridge bung 48. This may conveniently be done by fittinga micro-switch 51, such as a dome contact switch to a free end of theplunger 50.

[0059] Since the exact position of the bung 48 can be calculated withreference to the rear end stop 52, a number of units of medicamentstored within the cartridge 40 can be determined. Thus a half empty orincorrectly filled cartridge 40 may be used with the injector 2 of thepresent invention. The electronic control unit having determined thenumber of units stored within the cartridge preferably will not allow adosage larger than that remaining to be dialled up for dispense.

[0060] Alternatively, user interface software as part of the electroniccontrol unit can aid the user to split the required dose across acartridge changeover. For example, if the user is due to take a thirtyunit dose but only twenty units remain in the injector 2, then the usercan dispense the twenty units, replace the cartridge 40 and the injector2 will automatically offer the user ten units as the ‘outstandingbalance’ from the first dose. If the user does not take the ‘outstandingbalance’ (or other dose size) within a prescribed time, then theinjector 2 will revert to the normal display status. In such a case, theinjector history may record a ‘split dose’ as a single dose (being thetotal of the split doses) so long as the doses are taken within aprescribed time. Alternatively, the user may choose to take the firstpart of the dose and then cancel the second part of the dose rather thanrely upon the time out feature described above. This action will berecorded as part of the injector history information.

[0061] The drive mechanism 42 preferably operates at a constant speedduring dispense. However, at the start of each new cartridge 40 a slowerspeed may be appropriate to increase the force available to overcomestiction of the bung 48 in the cartridge 40. Alternatively, the speed ofdispense may be controlled to suit the comfort of the user.

[0062] In addition, the drive mechanism may be able to operate at avariable speed. In such a case, the injector 2 will be adapted to detectresistance to dispensing, for example if the medicament, i.e. insulin,is cold it may become more viscous and so provide greater resistance todispense. The drive mechanism can then slow to deliver more output forceand then stop if this has no effect upon the effective dispense action.In other words if, for example, the resistance to dispensing is due amechanical problem in the injector then the electronic control unit willswitch off the drive mechanism, and thus not dispense, rather than seekto dispense further medicament.

[0063] Due to the use of an electromechanical drive, the dispense actionis initiated by the user operating a switch. This means that the forcerequired to operate the dispense button can be optimised for the comfortand ergonomic requirement of users.

[0064] The drive mechanism 42 may additionally comprise a 1 bit encoder(for example an inductive transducer mounted at a first stage in thegear train 56) to detect slipping of the motor. Thus, should the drivemechanism 42 become jammed, this can be detected, the electronic controlunit can halt the drive mechanism 42 and indicate to the user that anerror has occurred.

1 An injection device for injection of a medicament from a firstmedicament cartridge 40, the injection device comprising a drivemechanism 42 for selectively dispensing the medicament from the firstmedicament cartridge 40, a dial dose mechanism 12,14 by which a user maydetermine a required dose of medicament to be dispensed, an electroniccontrol unit for controlling the operation of the drive mechanism 42 inresponse to the dial dose mechanism 12,14 and a display panel 10, inwhich when an insufficient amount of medicament remains in the firstmedicament cartridge 40 to enable the required dosage to be dispensed,the insufficient amount of medicament may be dispensed at the discretionof the user, the electronic control unit storing a value correspondingto a difference between the required dose and the insufficient amount ofmedicament, the value being presented to the user on the display panel10 as a first amount of medicament to be dispensed from a replacementmedicament cartridge following replacement of the first medicamentcartridge 40 with the replacement medicament cartridge. 2 An injectiondevice according to claim 1, characterised in that when the first amountof medicament is not dispensed within a predetermined time periodfollowing replacement of the first medicament cartridge with thereplacement medicament cartridge the electronic control unit resets toallow the user subsequently to operate the dial dose mechanism 12,14 todial a new required dose. 3 An injection device according to claim 2,characterised in that within the predetermined time period the user mayreset the electronic control unit to allow the user to operate the dialdose mechanism 12,14 to dial the new required dose. 4 An injectiondevice according to claim 1, in which the electronic control unitrecords a history of the dispensing of doses of medicament,characterised in that when the first amount of medicament is dispensedwithin a predetermined time period of dispensing the insufficient amountof medicament, the electronic control unit records the dispensing of theinsufficient amount and the first amount as a single dose.